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Vitamin K

Little-known but essential, vitamin K helps blood to clot. Most vitamin K is produced by bacteria in the gut, although there are also a few vitamin K-containing foods.

How much vitamin K do we need?

Age (years)

AI* Vitamin K (µg/day)

Infants

7-12 months

2.5

Children

1-4

25

4-8

35

9-13

45

14-18

55

Men

19-70+

70

Women

19-70+

60

Pregnant and breastfeeding women

14-50

60

Who needs more and why?

It is highly recommended that all babies are given a Vitamin K injection at birth. Babies have low levels of this vitamin as they have less bacteria in their gut where Vitamin K would be made and babies do not receive enough Vitamin K from their Mothers. Without the Vitamin K injection babies are at great risk of serious bleeding and developing a rare bleeding disorder.

Which foods contain vitamin K?

Vitamin K is found in green, leafy vegetables (such as spinach, broccoli, brussels sprouts, cabbage, lettuce), soybean and canola oils. Some milk products are fortified with vitamin K. However most vitamin K is produced by bacteria in the gut.

Medications and vitamin K

Warfarin is a blood thinning medication given to people to reduce the risk of blood clots forming in their body, which is the direct opposite action of Vitamin K which clots blood. People taking warfarin need to keep the amount of Vitamin K from foods and supplements in their diet constant. If the levels of Vitamin K consumed vary significantly then medication levels need to be changed to match this. This needs to be discussed and monitored by a doctor with support from a registered dietitian or nutritionist. Such changes may occur:

during summer if more salad greens, are being eaten

when certain high vitamin K vegetables are in season, such as Brussels sprouts

if cooking oil is changed to canola or soya which are both high in Vitamin K